Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $214.28   7.313%   $229.9503   $229.95   $229.95   $230.00  
  Purchase #2 $53.69   11.653%   $59.9465   $59.95   $59.95   $59.90  
  Purchase #3 $183.31   12.169%   $205.617   $205.62   $205.60   $205.60  
  Purchase #4 $41.92   12.478%   $47.1508   $47.15   $47.15   $47.20  
  Purchase #5 $17.67   9.235%   $19.3018   $19.30   $19.30   $19.30  
  Purchase #6 $56.57   12.537%   $63.6622   $63.66   $63.65   $63.70  
  Purchase #7 $126.34   7.591%   $135.9305   $135.93   $135.95   $135.90  
  7 purchase totals = $693.78       $761.5591   $761.56   $761.55   $761.60